Air Atmospheric Pressure Plasma Jet Research Articles

DISCHARGE DUTY CYCLES EFFECTS OF 20 KHZ AIR ATMOSPHERIC PRESSURE PLASMA JET ON METHYLENE BLUE SOLUTION DEGRADATION

The degradation of methylene blue (MB) using air atmospheric pressure plasma jet (air APPJ) in contact with liquid was proposed. In this study, an AC-driven air APPJ using three discharge duty cycles (30%, 50%, and 80%) of a neon transformer was investigated. In each discharge duty cycle, the ignition and extinguishment phases were characterized. The constituent particles of the air APPJ in the gas phase were observed by an optical emission spectrophotometer (OES). The OES results of all discharge duty cycles found the NO (A-X) bands, •OH radical, N2 second positive system, N2 first negative system, N+, N, and O. The emission spectra produced by the discharge duty cycle of 80% were the highest relative intensity. The effects of the different discharge duty cycles on the acidity and conductivity of water with and without MB were also determined. The complete dye degradation within 30 min was obtained in the discharge duty cycle 80%, which played an essential role in carrying reactive species from the gas phase to the liquid phase, thus promoting the degradation of MB. The best reaction kinetic rate k is 0.1692 min-1, which is six times compared to discharge duty cycle 50%.

Experimental investigation of an atmospheric pressure plasma jet as an ion source for on-site mass-spectrometry analysis of nonvolatile solid samples: the integration effect of thermal desorption and ionization

This work reported an air atmospheric pressure plasma jet served as an ion source for nonvolatile solid analysis, which allows a unique capability to achieve thermal desorption and ionization simultaneously without complex devices, inert gas, or solvents. Owing to precise amount of heat generated by plasma jet, nonvolatile analytes were thermally released from solid surfaces without the assistance of secondary desorption equipment. According to the mass spectra and Fourier transform infrared spectrum, [M + H]+ and [M + NO3]− ions were the major analyte ions in the positive-ion and negative-ion modes, respectively. The applied voltages, discharge currents, and gas temperatures of plasma jet were measured, and found to be positively correlated with the mass spectra signal intensity of the samples, while the added resistances and gas flow rate were negatively correlated with the signal intensity. The influence mechanisms of analytes natures coupling physical parameters of plasma jet on detection performance were revealed. The prospect of quantitative testing was confirmed by the linear relationship between the peak intensity and sample mass.

Numerical study on the production and transport of O and OH in a helium–humid air atmospheric pressure plasma jet interacting with a substrate

In this paper, the spatiotemporal developments of OH and O density in an atmospheric pressure helium–humid air plasma jet, both along the effluent and in particular close to the substrate surface, are evaluated under different governing parameters by performing two-dimensional numerical simulation. The results show that reducing the gas flow velocity can increase its density and shorten delivery time to the substrate surface. However, in different jet propagation stages, the dependences of the density distributions of two species on the gas flow speed are different. Before the plasma jet impinges the substrate surface, the O atom has a relatively higher density throughout the jet channel at low gas flow velocity; the increase in the flow velocity makes the peak O density shift to the jet head, whereas the OH radical is mainly distributed near the tube nozzle area and is almost unaffected by gas flow velocity. When the plasma jet moves along the substrate surface, increasing flow speed has little influence on the O density distribution but results in a longer spread length of OH along the substrate surface. By changing the relative permittivity of the substrate, it is found that both the densities and the axial extension lengths of O and OH increase with the relative permittivity, while the radial spread length over the substrate surface decreases. An earlier delivery of reactive species to the surface can be observed for the larger permittivity. The causes for these behaviors are also analyzed and discussed.

Enhancement Propagation of Protocorms in Orchid (Cymbidium tracyanum L. Castle) by Cold Atmospheric Pressure Air Plasma Jet

Propagation of orchid (Cymbidium tracyanum L. Castle) treated by using an air cold atmospheric pressure plasma jet at room temperature was investigated. The peak-to-peak voltage discharge and flow rate of the air atmospheric pressure plasma jet were set at 10.5 kV and 10 L/min, respectively. The constituent particles of the air cold atmospheric pressure plasma jet were revealed by optical emission spectroscopy. At the end of the jet nozzle, the constituent particles were observed, such as hydroxyl radical ˙OH, N2 first negative system (N2 1 −), N2s positive system (N2 2 +), and atomic oxygen. The average size, average number of buds, fresh and dry weights simultaneously increased by cold air plasma treatment compared with the control ones. The highest positive effects of treated protocorms on average size, average number of buds, fresh and dry weight were significantly improved by 238.2, 475.9, 85.6, and 152.5%, respectively. The transmission electron microscope showed the cytoplasmic cell wall in orchid protocorm disturbed by air cold plasma. Thus, the effects of constituent particles of air plasma might attack in the cell wall of protocorm leading to cell loosening, which improved elongation and released bud dormancy. These results indicated that the propagation of orchid protocorms depended on the effects of air cold plasma treatment with different plasma time durations.

Deposition of TiO2 Thin Films on Wood Substrate by an Air Atmospheric Pressure Plasma Jet

In the present work, titanium dioxide (TiO2) coatings were deposited on wood surfaces by an atmospheric pressure plasma jet using titanium tetraisopropoxide (TTIP) as a precursor to improve the wood’s stability against ultraviolet (UV) light and its moisture resistance capability. The surface topology and morphology of the wood specimens were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface chemical compositions of the specimens were characterized by X-ray photoelectron spectroscopy (XPS) and by Fourier transform infrared (FTIR) spectroscopy. The wettability of the coated wood was investigated by measuring the sessile contact angle. SEM and AFM showed the presence of small globules of TiO2 with some areas agglomerated on the coated wood surface. The coated surface roughness increased with increasing deposition time. FTIR analysis showed the existence of a Ti–O–Ti band at 800–400 cm−1 on the coated wood surfaces. The results obtained from FTIR were confirmed by XPS measurements. The hydrophilic wood surfaces were transformed to become hydrophobic or superhydrophobic after coating with TiO2, depending on the deposition parameters. The changes of colour during UV-exposure for both uncoated and coated wood specimens were measured using the CIELab colour system. The TiO2 coated wood became more resistant to colour change after UV radiation exposure than did untreated wood.

Modeling and experimental investigation of a Wurster type fluidized bed reactor coupled with an air atmospheric pressure plasma jet for the surface treatment of polypropylene particles

Modeling and experimental investigation of a Wurster type fluidized bed reactor coupled with an air atmospheric pressure plasma jet for the surface treatment of polypropylene particles

Modeling and experimental investigation of a Wurster type fluidized bed reactor coupled with an air atmospheric pressure plasma jet for the surface treatment of polypropylene particles

Polypropylene (PP) particles are used for various purposes, however, the good mechanical properties of PP are counterbalanced by a poor wettability. The wettability of PP particles was therefore improved by an atmospheric pressure blown‐arc air plasma jet treatment in a new designed homemade Wurster fluidized bed reactor (Wurster‐FBR). This reactor, was used to treat 200 g of particles per batch. The surface free energy of PP particles determined by the Zisman method showed an increase from 30.7 to 38.6 mN m−1 after 120 s of treatment. XPS results showed a 5% increase of the atomic concentration of oxygen on the surface of the treated particles. In order to describe the process, a 2D axisymmetric non‐isothermal k‐ϵ turbulent model was used to determine the velocity field, pressure, and temperature profile of the gas phase inside the reactor. Furthermore an Eulerian‐Eulerian multiphasic CFD model was added to determine the dynamics of the particles inside the reactor, and the results were compared with fast imaging, thermocouple, and anemometry measurements. These investigations are very important to monitor the homogeneity of the particle treatments, to determine the average effective treatment time for each particle and to avoid overheating of thermally sensitive PP.

Comparative Adhesion, Ageing Resistance, and Surface Properties of Wood Plastic Composite Treated with Low Pressure Plasma and Atmospheric Pressure Plasma Jet.

Wood plastic composites (WPCs) have poor adhesion properties due to their high surface concentration in non-polar polymers. In this work, two different plasma surface treatments, low pressure plasma (LPP) and atmospheric pressure plasma jet (APPJ), are proposed to increase the surface energy and adhesion property of WPC made with polyethylene (PE-WPC). After optimizing the conditions for each plasma surface treatment, the surface modifications and adhesion of PE-WPC treated with LPP and APPJ were compared. The optimal surface modifications of PE-WPC were obtained by treatment with Argon (Ar): Oxygen (O2) LPP for 90 s, and with air APPJ by using a plasma nozzle-WPC surface distance of one centimeter and speed of platform of one meter per minute. Both plasma treatments produced similar chemical modifications and surface energies on the PE-WPC surface. The ablation was more important for Ar:O2 LPP treatment, and the air APPJ treatment produced more extensive chemical modifications and more homogeneously removal of the wood component of the surface, rendering the polymer surface smoother. Adhesion of PE-WPC was similarly improved by treatment with both plasmas, from 56 N/m in the as-received to 92–102 N/m in the plasma treated PE-WPC joints. The influence of ageing at 24 °C and 40% relative humidity of the adhesive joints made with PE-WPC surface and treated with Ar:O2 LPP and APPJ plasmas was studied. In the joints made with plasma-treated PE-WPC aged under open air for more than one day, the adhesion decreased. An adhesive strength near to that of the joint made with the as-received PE-WPC was obtained after six days. However, if the adhesive joint was created immediately after plasma treatment and peeled at different times, the adhesion was maintained and even increased, and the hydrophobic recovery of the plasma-treated PE-WPC surface was inhibited.

Redox performance of Na-modified Fe2O3/Al2O3 with syngas as reducing agent in chemical looping combustion process

The redox performances of 1–10 wt% Na-modified Fe2O3/Al2O3 oxygen carrier from seawater were investigated using syngas/air as reactive gases in the thermogravimetric analyzer (TGA) and lab-scaled semi-fluidized bed reactor (semi-FzBR). NaNO3(aq) as the source of sodium dopants to prepare Na-contained solution was implemented by an air atmospheric pressure plasma jet (Air-APPJ) process, which can increase the feasibility of seawater. For the prepared samples, the materials properties, including crystalline phases, surface morphologies, surface areas, and attrition loss performances were well correlated with the Na contents. The results indicated that the poor reduction kinetics and attrition resistance were obtained with the Na adjunction over 5 wt%, attributing to the sintering issue on excessive phases of Na2(Al, Fe)12O19 and Na(Al, Fe)O2 solid solution in the samples. Therefore, the slight incorporation of Na content in the Fe2O3/Al2O3 samples which improved the reduction rate was proved as the candidate oxygen carriers. Particularly, the Na content with 1 wt% in Fe2O3/Al2O3 sample (Na1FA32) can significantly promote the reduction behavior, thermal stability, and attrition resistance as compared to the raw Fe2O3/Al2O3 oxygen carrier. It is environmentally beneficial to use the Na1FA32 as oxygen carrier in a practical chemical looping combustion process.

Carbon-free SiOx ultrathin film using atmospheric pressure plasma jet for enhancing the corrosion resistance of magnesium alloys

This study describes the use of tetraethylorthosilicate (TEOS) as the precursor to deposit carbon-free silica (SiO2) dense film as the anti-corrosion layer on the surface of AZ91D magnesium alloys using an air atmospheric pressure plasma jet (APPJ). From the contact angle measurements, APPJ-deposited silica film on AZ91D represents a more hydrophobic property with a lower total surface free energy of 31.3 mN/m. XPS depth profile analyses revealed the chemical compositions (O and Si) were uniformly distributed through the bulk of the deposited films with a thickness of 207 nm, which also comprises of carbon-free SiO2 ultrathin films. The electrochemical impedance spectroscopy (EIS) measurements and corrosion morphologies of 14-day immersion test of deposited films and AZ91D samples in 3.5 wt % NaCl solution are also investigated. The results indicate ultrathin silica coating not only alter the surface property, but also improve the corrosion resistance of AZ91D magnesium alloys.

A facile method for sodium-modified Fe2O3/Al2O3 oxygen carrier by an air atmospheric pressure plasma jet for chemical looping combustion process

The use of seawater as catalytic agents for hematite (Fe2O3) as oxygen carrier in chemical looping combustion process is attractive, because of its abundance and low cost. Unfortunately, seawater itself with major NaCl compound under reactive species accompanying the volatilization of chlorine-containing gases probably lead to the corrosion on reactors during the combustion process. In this study, the feasibility evaluation of sodium dopants extracted from seawater as an effective catalytic agent via an air atmospheric pressure plasma jet (Air-APPJ) is performed, and as such it is combined with Fe2O3/Al2O3 to assess any possible enhancement on the reduction kinetics. The sodium-contained solutions, NaNO3(aq) and NaCl(aq), as precursors are used to prepare the sodium dopants due to the evaporation-decomposition of water and dissolved salts via plasma discharge reaction. The sodium-modified Fe2O3/Al2O3 oxygen carrier can significantly promote the efficiency of the carbon capture efficiency and CO2 yield. Especially for the NaCl(aq) as precursor in an Air-APPJ system, the high carbon capture efficiency, CO2 molar fraction and CO2 yield around 0.96, 0.95 and 0.91 after fifty redox cycle for the sodium-modified Fe2O3/Al2O3 oxygen carrier are achieved. It can be anticipated that the sodium-modified Fe2O3/Al2O3 from seawater by an Air-APPJ system as an oxygen carrier candidate in a reversible CLC process would be notably attractive.

Open air plasma deposited antimicrobial SiOx/TiOx composite films for biomedical applications

Abstract Open air atmospheric pressure plasma jet (APPJ) enhanced chemical vapour deposition process was used to deposit biocompatible SiOx/TiOx composite coatings. The as deposited films are hydrophilic and show visible light induced photocatalytic effect, which is a consequence of the formation of defects in the TiOx structure due to the plasma process. This photocatalytic effect was verified by the demonstration of an antimicrobial effect under visible light on E. coli as well as by degradation of Rhodamine B. The films are non-cytotoxic as shown by the cytocompatibility tests. The films are conductive to cell growth and are stable in DMEM and isopropanol. The structural evaluation using SEM, EDS and XPS shows a dispersion of TiOx phase in a SiOxCyHz matrix. These analyses were used to correlate the structure-property relationship of the composite coating.

Protection of active implant electronics with organosilicon open air plasma coating for plastic overmolding

Abstract To overcome challenges for manufacturing of modern smart medical plastic parts by injection molding, e.g. for active implants, the optimization of the interface between electronics and the polymer component concerning adhesion and diffusion behavior is crucial. Our results indicate that a nano-sized SiOxCyHz layer formed by plasma-enhanced chemical vapour deposition (PE-CVD) via open air atmospheric pressure plasma jet (APPJ) and by use of a hexamthyldisiloxane (HMDSO) precursor can form a non-corrosive, anti-permeable and biocompatible coating. Due to the open air character of the APPJ process an inline coating before overmolding could be an easy applicable method and a promising advancement.

Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet

Atomic oxygen number density [O] is measured in an air atmospheric pressure plasma jet (APPJ) using two-photon absorption laser induced fluorescence (TALIF). Gas flow is fixed at 8 slpm, the RF power coupled into the plasma jet varied between 5 W and 20 W, and the resulting changes in atomic oxygen density measured. Photolysis of molecular oxygen is employed to allow in situ calibration of the TALIF system. During calibration, O2 photo-dissociation and two-photon excitation of the resulting oxygen atoms are achieved within the same laser pulse. The atomic oxygen density produced by photolysis is time varying and spatially non-uniform which needs to be corrected for to calibrate the TALIF system for measurement of atomic oxygen density in plasma. Knowledge of the laser pulse intensity I0(t), wavelength, and focal spot size allows correction factors to be determined using a rate equation model. Atomic oxygen is used for calibration and measurement, so the laser intensity can be increased outside the TALIF quadratic laser power dependence region without affecting the calibration reliability as the laser power dependence will still be the same for both. The atomic O density results obtained are not directly benchmarked against other known density measurement techniques. The results show that the plasma jet atomic oxygen content increases as the RF power coupled into the plasma increases.

Effect of non-thermal air atmospheric pressure plasma jet treatment on gingival wound healing

Non-thermal atmospheric pressure plasmas have been applied in the biomedical field for the improvement of various cellular activities. In dentistry, the healing of gingival soft tissue plays an important role in health and aesthetic outcomes. While the biomedical application of plasma has been thoroughly studied in dentistry, a detailed investigation of plasma-mediated human gingival fibroblast (HGF) migration for wound healing and its underlying biological mechanism is still pending. Therefore, the aim of this study is to apply a non-thermal air atmospheric pressure plasma jet (NTAAPPJ) to HGF to measure the migration and to reveal the underlying biological mechanisms involved in the migration. After the characterization of NTAAPPJ by optical emission spectroscopy, the adherent HGF was treated with NTAAPPJ or air with a different flow rate. Cell viability, lipid peroxidation, migration, intracellular reactive oxygen species (ROS), and the expression of migration-related genes (EGFR, PAK1, and MAPK3) were investigated. The level of statistical significance was set at 0.05. NTAAPPJ and air treatment with a flow rate of 250–1000 standard cubic centimetres per minute (sccm) for up to 30 s did not induce significant decreases in cell viability or membrane damage. A significant increase in the migration of mitomycin C-treated HGF was observed after 30 s of NTAAPPJ treatment compared to 30 s air-only treatment, which was induced by high levels of intracellular reactive oxygen species (ROS). An increase in migration-related gene expression and EGFR activation was observed following NTAAPPJ treatment in an air flow rate-dependent manner. This is the first report that NTAAPPJ treatment induces an increase in HGF migration without changing cell viability or causing membrane damage. HGF migration was related to an increase in intracellular ROS, changes in the expression of three of the migration-related genes (EGFR, PAK1, and MAPK1), and EGFR activation. Therefore, NTAAPPJ for gingival tissue healing is a promising method for health and aesthetic outcomes.

Air atmospheric pressure plasma jet pretreatment for drop-wise loading of dexamethasone on hydroxyapatite scaffold for increase of osteoblast attachment.

Periodontal disease affects alveolar bone resorption around the involved teeth. To gain bone height, bone graft materials have been widely used with drug carriers. Application of an atmospheric pressure plasma jet (APPJ) treatment is widely studied due to its ability to change surface characteristics without topographical change. The aim of this study is to identify whether the air APPJ (AAPPJ) treatment before drop-wise loading performance could change loaded amount of dexamethasone, and induce increase of cell attachment and proliferation. The results suggested that AAPPJ treatment decreased the contact angle down to about 13 degrees, which increased gradually but significantly lowered at least 4 days compared to no-treated group. After AAPPJ treatment, hydrocarbon was removed with change of zeta potential into positive charge. However, the AAPPJ treatment did not change the quantity or releasing profile of dexamethasone (p > 0.05). Confocal analysis combined with DNA proliferation analysis showed increase of osteoblast attachment and proliferation. Hence, AAPPJ could be a useful pretreatment method before drop-wise loading on HA scaffold with dexamethasone for increase of osteoblast attachment.

Air atmospheric-pressure plasma-jet treatment enhances the attachment of human gingival fibroblasts for early peri-implant soft tissue seals on titanium dental implant abutments

Objective. Although dental implants are commonly used for tooth restoration, there is a lack of studies of treatment regimens for preventing extra-oral infection and decreasing osseointegration failures by establishing early peri-implant soft tissue seals on titanium dental implant abutments. In this study, air atmospheric-pressure plasma-jet (AAPPJ) treatment was applied to titanium disks to assay the potential for early peri-implant soft tissue seals on titanium dental implant abutment. Materials and methods. After titanium disks were treated with AAPPJ for 10 s at 250, 500, 1000 and 1500 sccm, surface analysis was performed; the control group received air only or no treatment. Human gingival fibroblasts (HGF) were seeded onto the specimens for evaluating cell attachment and proliferation and adherent-cell morphology was visualized via confocal microscopy. Results. In AAPPJ-treated specimens, the water contact angle decreased according to increased flow rate. Oxygen composition increased in XPS, but no topographical changes were detected. The effect of AAPPJ treatment at 1000 sccm was apparent 2 mm from the treated spot, with a 20% increase in early cell attachment and proliferation. Adherent HGF on AAPPJ-treated specimens displayed a stretched phenotype with more vinculin formation than the control group. Conclusions. Within the limitations of this study, the results indicate that AAPPJ treatment may enhance the early attachment and proliferation of HGF for establishing early peri-implant soft tissue seals on titanium dental implant abutments with possible favorable effects of osseointegration of dental implant.

Cell immobilization on polymer by air atmospheric pressure plasma jet treatment

The study of cell immobilization on delicate polymer by an air atmospheric pressure plasma jet (AAPPJ) is required for its medical application. The aim of this study was to evaluate whether AAPPJ treatment induce cell immobilization effect on delicate polymers without significant change of surface roughness by AAPPJ treatment. After surface roughness, dynamic contact angle, and chemical characteristics were investigated, the immobilization effect was evaluated with the mouse fibroblast L929 cell line. Surface roughness change was not observed (P > 0.05) in either delicate dental wax or polystyrene plate (PSP) as advancing and receding contact angles significantly decreased (P < 0.05), thanks to decreased hydrocarbon and formation of oxygen-related functional groups in treated PSP. Adherent L929 cells with elongated morphology were found in treated PSP along with the formation of immobilization markers vinculin and actin cytoskeleton. Increased PTK2 gene expression upregulated these markers on treated PSP.

Highly efficient photocatalytic TiO2 coatings deposited by open air atmospheric pressure plasma jet with aerosolized TTIP precursor

A simple method to deposit photocatalytic TiO2 coatings, at a high rate (20–40 µm s−1), and with a high porosity, is reported in this paper. This method, which allows the treatment of membranes (with an 800 nm pore size), is based on the introduction of a liquid precursor sprayed into an open-air atmospheric pressure plasma jet (APPJ). The photocatalytic activity of the TiO2 thin films prepared by APPJ have been compared with our best N-doped TiO2 thin films, deposited by reactive radio frequency (RF) magnetron sputtering, previously reported in the literature. The morphology, chemical composition, photoelectrochemical, and photocatalytic properties of the coatings have been studied in this paper. Significant control of the porosity and crystallinity was achieved by varying the deposition parameters and the annealing temperature. Under optimized conditions, the TiO2 coatings deposited by APPJ are characterized by a higher photocatalytic activity as compared to the optimized thin films deposited by RF sputtering. This difference can be explained by the higher specific surface of the APPJ coatings. Finally, the most interesting characteristic of this APPJ-liquid spray process is its capacity to treat membranes without blocking the pores, and to produce photocatalytic membranes which can efficiently combine filtration and photocatalysis for water treatment.

Development of hydrophilic dental wax without surfactant using a non-thermal air atmospheric pressure plasma jet

Dental wax (DW), a low-melting and high-molecular-weight organic mixture, is widely used in dentistry for forming moulds of teeth. Hydrophilicity is an important property for DW, as a wet dental investment is used to surround the wax before wax burnout is performed. However, recent attempts to improve the hydrophilicity of DW using a surfactant have resulted in the reduced mechanical properties of the dental investment, leading to the failure of the dental restoration. This study applied a non-thermal air atmospheric pressure plasma jet (AAPPJ) for DW surface treatment and investigated its effect on both DW hydrophilicity and the dental investment's mechanical properties. The results showed that the application of the AAPPJ significantly improved the hydrophilicity of the DW, and that the results were similar to that of cleaner-treated DW using commercially available products with surfactant. A surface chemical analysis indicated that the improvement of hydrophilicity was related to an increase in the number of oxygen-related bonds on the DW surface following the removal of carbon hydrate in both AAPPJ and cleaner-treated DW. However, cleaner treatment compromised the mechanical property of the dental investment when the dental investment was in contact with the treated DW, while the AAPPJ treatment did not. Therefore, the use of AAPPJ to treat DW is a promising method for accurate dental restoration, as it induces an improvement in hydrophilicity without harming the dental investment.